Amphiphilic Block Copolymers for Flocculation and Hydrophobization of Legacy Waste Suspensions in Flotation Driven Dewatering Operations
- School of Chemical and Process Engineering, University of Leeds, Leeds, West Yorkshire (United Kingdom)
There exists a degrading legacy fuel pond at the Sellafield site (UK), known as the First-Generation Magnox Storage Pond (FGMSP). After being placed into a passive care and maintenance regime resulting in a long storage period, the fuel rods, primarily their cladding, corroded in the pond forming magnesium hydroxide based sludges and suspended material. These ponds are a grave concern to the British government in terms of hazard and risk reduction. Therefore, decommissioning of these ponds is a top priority beginning with the contaminant retrievals process [1]. The pond has accumulated significant quantities of waste materials amongst the skips of fuel, including but not limited to: large inventories of corroded Magnox sludge, fuel rod fragments, metal fragments (from fuel skips), concrete degradation products (from the pond infrastructure), wind-blown sand, and other materials such as bird guano and animal remains. This challenge requires a chemically robust technology to complete sludge retrievals [2]. As nuclear is different, a more stringent process operation criteria is required. From the criteria, flotation was selected as a viable technology. Flotation involves the application of collector molecules which modify the hydrophobicity of suspended particles allowing them to adsorb to rising bubbles. As some particles lack inertia for flotation due to their size, dual flocculant/collector agents can be deployed for greater particle recovery, in this case, amphiphilic diblock copolymers. Two copolymers of Poly(acrylic acid)-b-poly(n-butyl acrylate) (or PAA-b-PnBA), of different hydrophobic chain lengths (PBA) were synthesized for flotation campaigns. Flotation has shown promise to be a valuable rapid dewatering strategy for decommissioning of legacy waste ponds whilst upholding the required operational criteria. This research has shown: PAA-b-PnBA copolymers promote flocculation of Mg(OH){sub 2} particulates. Diblock copolymers retain more fluid than traditional surfactant based collectors wrt. relative particulate recovery performance- where longer PnBA chain length polymers performed best. Performance appears to be hydrodynamically limited due to over-flocculation of Mg(OH){sub 2}. Potential to combine with sedimentation for high particle recovery with low fluid carryover.
- Research Organization:
- WM Symposia, Inc., PO Box 27646, 85285-7646 Tempe, AZ (United States)
- OSTI ID:
- 23030270
- Report Number(s):
- INIS-US-21-WM-20-P20605; TRN: US21V2016070622
- Resource Relation:
- Conference: WM2020: 46. Annual Waste Management Conference, Phoenix, AZ (United States), 8-12 Mar 2020; Other Information: Country of input: France; 3 refs.; available online at: https://www.xcdsystem.com/wmsym/2020/index.html
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ACRYLATES
ACRYLIC ACID
CLADDING
CONCRETES
COPOLYMERS
DECOMMISSIONING
FLOCCULATION
FLOTATION
FLUIDS
FUEL RODS
MAGNESIUM HYDROXIDES
MAGNOX
METALS
PARTICULATES
RADIOACTIVE WASTES
SEDIMENTATION
SLUDGES
SURFACTANTS
SUSPENSIONS
WATER REMOVAL